Another successful top hat build

[rumwrks]

  :D :D :D :D :D :D

First let me say thanks to all for posting the great ideas and excellent pictures and mostly to Phil for putting this idea and plan out there to begin with!

Nothing really new on mine and unfortunately I didn't take a lot^wany of pictures during the build as I was racing to get it done before some equipment showed up.  However I did try a few things along the way that I liked and a few I didn't like that I thought I'd pass on in case they prove useful for anyone else.

Started with the ubiquitous  harbor freight 2hp unit and added a Wynn 35a nano filter.  My barrel is a recycled bleach barrel I got from the local recycling place.  The price for taking one barrel was "take two", so I have an extra 30g barrel to do something with.  It pays to figure out where all the friendly local junkyards are.  Had to rasp the top "flat" (or close, some weather stripping makes up the difference), cut the top out and plug a few weep holes.

My build is a top hat made from 3/4" cabinet grade" (from HD, ok for shop cabinets I guess) plywood throughout.  The curved wall was made from the "death by a thousand cuts" and bend method.  The wall is set into a rabbet flush along the slot and glued in place with construction adhesive.  I skinned the inside of the wall with with sheet metal obtained from the ductwork section of HD (really easy, just cut to width with tin snips and construction adhesive in place, required two pieces so I overlapped them a smidge just past the curve on the inlet side).  Required a fair number of clamps to hold in place, but some strategically shaped/placed cauls could make up the difference.  The side sheet metal projects slightly (1/32 or so) below the bottom plate (its notched to fit flush with the bottom on the non slotted side) and was filed it "almost" flush on top (left a 1/100-2/100 sticking up to "seal" the top on).

For the floor/baffle (cut from one piece) I actually used 3/4 plywood but cut the slot 1/2" wider than it needed to be.  I routed a 45d chamfer on the bottom of the floating part and then skinned the top of the floor with more sheet metal with a 1/2" overhang.  The idea was that I'd get the strength of the plywood but the thin edge of the sheet metal to get decent separation.  This appears to be really solid and separates quite well (I've run both table saw sawdust and hand plane shavings through it no problem).  The impeller unit is simply "set" on top (they are actually both bolted to the stand..) so the intake run is super short/straight.  I used 5" stove pipe for the extension.  I tried a 5" to 6" reducer to try and increase the intake size a little, but that seemed to let more fine dust through (it was still really good but not as good as the straight 5").  I'll be watching the bell mouth builds with interest :D.  I think with a larger separator it would have been fine (my 30g plastic drum only allowed ~18" across inside). 

Currently I'm running a 6" inlet/duct, but am planning to drop that to 5" once I get some hose in.  Preliminary tests indicate minimal pressure drop at the distances I'm running (measured by the "from how far away can I suck up a pile of sawdust" method, no anemometer but still accurate enough in relative terms) and somewhat better separation, its also a more natural size for my machines (mostly 120mm).

I wanted the whole assembly to be movable as I'm still figuring out my machine layout and the barrel + everything wouldn't fit on the original HF base, so I built a new base/platform out of angle iron (mostly recycled bed frames I got for free - watch the local freecycle), some 1/2" plywood for the floor and some old casters I had laying around.  The top hat and impeller/motor assembly are both bolted to a stack of glue lam 2x3's that are bolted to 1.5x1.5" angle iron uprights.  I put a pair of angled cross brace to from the back to the front but just left those "floating" on the bottom (the top hat is also bolted to these to tie the front of it and the impeller together more).  The angle brace fronts sort of "clip" onto the front of the base with the way the angle iron goes together holding it in place but still allowing the the whole top hat + impeller to float a little.  This allows me to tilt the assembly back a 1/2" and squeeze the barrel underneath.   The inlet and outlet are on the same side, this puts the inlet right under the filter pushing the original plastic bag aside which is great for space efficiency and I can still get the bag on/off if need be (doesn't look like I'll have to worry about that).   I was planning on doing some sort of "lifter" mechanism to hold the barrel in place but found that just positioning it correctly, turning the unit on (to suck it up) and then wedging a couple of slats under it works quit well so may not bother with anything more complicated.

Overall performance is pretty spectacular.  My initial worst case test run was to sweep up all of the sawdust from the cuts for making the bendy piece and other pieces (roughly a 1' tall cone of pretty fine dust) and shove a 6" flex pipe into it, dump and repeat.  I had taped the original cloth bag over the outlet (it was still clean) to see how much fines actually came though.  With the 5"-6" expansion you could see "puffs" of dust on the outlet, with the straight 5" - nothing really visible and the dust on the bag didn't seem to increase measurably.  Yesterday I peeled a bunch of cedar shavings off with some hand planes (was sharping up/testing some old ones so was mostly just goofing around) and shoved them in the 6" outlet, nothing escaped.

Its not the prettiest beast, but performance is all I could ask for and more!  Thanks again all for the great details and information.

I'll try to take a couple of snapshots this week if I remember/have time around my other projects.

[Don_Z]

I bet you have been wondering why are all these people lurking but nobody seems to have anything to say? Post some pictures of your success, I am sure we would all like to see.  ;D

[retired2]

I've been waiting for your photos too!

I like what you did with the separator floor and the very thin edge on the baffle drop slot.  I don't know anyone that has tried that one, but according to Phil thinner is better. 

I also like covering the interior walls with sheet metal.  I think sheet metal is the way to go.  I used plexiglass because I wanted to see what was going on inside the separation chamber while I was testing the bellmouth.  A see-through wall sure is sexy and it's mesmerizing to watch, but from a friction point of view I think galvanized sheet metal may be the way to go.

I don't have the equipment to do any more testing of the bellmouth outlet, but the results of the testing I've done are now posted.  I think the data suggests it is worth giving it a try.  I'm also sold on a rectangular inlet.  The test video I shot shows very little or no turbulance where the two airstreams merge inside the chamber.

[rumwrks]

Sorry to be so slow with the pictures, but the machines I was building this for showed up so I've been busy getting them setup and .. well.. playing  ;D  Attached is a picture of the inside of the baffle, the bottom of the baffle (well a close up of one part) - before I routed it down and two pictures of the cart with the baffle assembly removed for maintenance.  Its not nearly as pretty as some of the builds I see here by a long shot - nice work guys, them things are sexy!

First the good news  :), it works great with the table saw.  No measurable dust showing up from that and lots of suction.

Now the bad news :(  I'm having some problems with the new planer, it worked fine with my lunchbox and heck even picked up a decent size pile of hand plane shavings fine.. but... the shear volume of long stringies from the new floor planer is overwhelming it (from my test board the shavings come off in a heavy stream of paper thin pieces about 1/4" wide and 4-5" long - impressive in a way).  They build up starting at the "far" end  of the slot and eventually wrap all the way back around to the entrance.  I may well be pushing the far end of what the capabilities of this config are, but its interesting to see how/if this works anyway.

I've tried a few things so far:

• Routed out the underside of the baffle to slim the whole thing down to about 1/4" and shaved the edge of the bevel on the underside a lot thinner.  This helped a little but not nearly enough.
• Opened up the slot, I'm pushing 1.5" now.  Still clogs, but I can get most of the way through a wide board before it clogs up.

I'm thinking I'll try polishing the edge of the baffle some more tomorrow, small nicks in the metal really seem to catch the planer shavings.  If that doesn't work... well.. heh.. not sure yet.  Might try widening the slot more, but I suspect that I'm reaching some upper limit on functionality there.  I'm also wondering if I can do "something" around where the slot ends to reduce the amount of shavings that catch there.

Worst case I figure I can re-engineer the whole thing and move the baffle over the bag and I'm not really behind much and have learned some stuff.

I am certainly open to ideas on tweaks though.

[retired2]

rumwrks,

As I look at your photos, a couple things come to mind.  First, the sheet metal baffle that I thought was a great idea, may be a case of too much of a good thing, at least in the case of stringy waste.  Long waste strips are going to be very susceptable to hanging up on a thin edge, especially at the end of the drop slot.  I don't think smoothing the edge of the metal baffle is going to help very much.  In your first photo it looks like there are some places near the end of the drop slot that could snag long shavings.  Also, your drop slot looks like it has a square end, with normal radiused corners.  That's what most of us have, and it works fine, but with long waste you might want to try filing the end of your drop slot into a semicircular shape.  It may or may not help.  I do not think you should open the slot any wider.

The second thing I noticed was that for 6" piping, the diameter of your separator does not look very big.  For comparison, my separator with 5" pipes is 19-5/8" I.D.  If I am right about yours being smaller, you could have a lot of turbulance at the inlet pipe because the recirculating air is converging at almost a right angle.  This turbulance could be contributing to the shavings hanging up because they are not being swept along in a smooth air stream.  See Reply #68 in my thread titled "5", Rectangular Inlet, Bellmouth Outlet, Top Hat Thien Separator".  That post describes, with a sketch, the issue I am talking about.

[dabullseye]

Try to smooth the edges with a stone or if you have some real bad sniper edges you might try to solder and smooth them out

[retired2]

rumwrks,

I just had another thought that might help and would be easy to try.  One reason for the "birds nests" forming at the end of the drop slot could be the result of the long shavings hitting the thin edge of the drop slop.  It is retained because a portion of the length is above the slot and a portion is below.  The thin edge of the baffle keeps the shaving from dropping into the waste drum, or releasing to make another trip around the separator.  Once, one piece of waste hangs up, soon a second clings to the first and so on until you have a clog.

What I would try is this.  Change the "knife" edge at the end of the drop slot to a very blunt rounded edge so that a piece of long stringy material has nothing to cling to.  It either drops through to the drum below, or is blown out of the slot for a another trip around.  I'm not sure what material to suggest using as a filler, but it should be something that dries hard and smooth and can be shaped with sandpaper or files.

Regards
retired2

[phil (admin)]

I'm not ignoring this, I'm still thinking on a solution...

[rumwrks]

Thanks for the ideas all, much appreciated.  I've made a few mods and gotten a little more meat out of it.  Its still clogging up but not quite as bad - and now its clogging differently, so I'm calling this progress of sorts.  At the very least I'm figuring some stuff out :D

Quick summary for others, I believe my main causes of failure thus far are:

• Planer+wood combo is insane, "normal" tools wouldn't be (and indeed weren't) a problem here.
• top hat is to small for chip volume
• the metal skin baffle is a bit fussy.  It has to be uber smooth on the edges to work with this type of shaving.

I think its a little hard to convey with words the sheer volume of shavings I'm getting here so I've attached a few more pics.  The first pic is of a handful to show the general consistency and type, they also tend to occasionally clump up a little on the way out of the joiner/planer, which doesn't help any.  The second is of one shaving, they are micro thin and that 5" shaving is about average length - some are actually longer (how the heck a straight blade planer makes shavings like that is still confusing/amazing me).  The final picture is of a pile from 2 passes with my test board (about 11" wide x 7' long) - thats a 12" rule sitting next to it for scale - each pass takes roughly 1 minute so figure 50% of that pile in one minute  :o.  After only ~8 thin passes the 30g barrel was 75% full albeit super fluffy...  I do realize that I'm pushing the far edge of normal here, this is kind of a worst case scenario as far as the type/volume of shavings go (and practically speaking I normally work with harder woods that would take lighter cuts and thus have less volume and break up into smaller pieces) - so I figure if I can beat this one.. I'll have no problems with anything else :D  I'm actually not 100% sure what type of wood this is - it was part of the pallet the joiner came on - looks and cuts like pine but is a bit whiter than I'd normally associate with pine and has no observable pitch spots.

I'm starting to think that the 30g drum is to small for a whole bunch of reasons  :o  Retired2 - you are correct my separator is smaller than yours, its only about 15.5" ID.  I definitely agree that the size likely isn't helping any.  Observing the airflow with a temporary short (8" long) inlet it seems to "swirl" pretty good, but having done a wee bit of fluid dynamics modeling in a previous life I know enough to know that I don't know much in that regard and that what I think I know usually ends up being wrong  ;D  Switching to a 5" inlet did actually appear to help the smoothness of the airflow some so you are probably on to something there.

What I've done so since last post:

• Polished the edge by draw filing and then stoning (twice actually - once before and then again after opening the slot more).  dabullseye you are definitely correct here. This appears to be very important with the metal plate (and this type of shaving - matters not at all with sawdust/chips), as the slightest rough spot definitely causes these little strips to catch.  While testing with small amounts of shavings I also found a spot about 1/2 way around that was causing a small catch, and thus eventual backup.  This irregularity was barely detectable by feel, so even the smallest catch definitely mattered and demonstrating how touchy this config is
• Dropped the inlet to 5" (finally got the parts), this seemed to help some and definitely seems like the way to go here.  While bigger is usually better... its definitely not true in this case.
• Opened up the slot to a full 1.5" (was closer to 1.25" as of last post once I carefully measured).  I believe this was not really optional with this shaving volume after having spent some time spent dumping handfuls of shavings into the inlet at about the rate the planer runs them in (I'm not sure, but suspect that with a bigger top hat a smaller slot may well work ok because you have more slot opening overall).  While doing this (or more accurately while carefully measuring for it) I found out that the slot was actually about 3/8" narrower at the end of the slot.   I'm pretty sure this was also causing problems.  Opening the slot also made the edge a bit thicker because I removed all of the overhang and went into the wood a smidge.  Observation indicates that the slightly wider may well have actually helped some, at least for shavings.  I tried the wider slot with a 6" inlet (just for fun) and was getting quite a bit of bypass with the sawdust test - that seems to have stopped once I switched to a 5" inlet.
• Polished the edge again ::).

So.. after doing that.. what I'm finding is that the slot is still getting clogged up with shavings but its not necessarily (or even usually) clogging up at the end, but more randomly around the edge.  I've taken multiple passes, shut down and observed the clog spot and its usually at a spot about opposite the inlet but does move around some.  It could be that I have a few spots with a smidge of variation in width or smoothness, but I'm starting to believe that its just a simple volume vs opening size problem at this point.  I ended up cutting the guards out of the impeller inlet so I could  finish a full pass without being completely gummed up.  Before doing that I had one pass completely fill the inside of the separator plumb full when the clog hit early :o  Interestingly removing the guards also seems to have slowed down the apparent clogging, my theory is that the continued airflow actually pulls the clumps back out and eventually clears them unless they are really jammed in place.

Currently my plan is to move up to a bigger drum (50g) and thus a bigger top hat.  This is at least partially because I'm coming to the conclusion that 30g - which seemed huge - isn't actually all that big in this case!  I was slightly concerned that the little HF unit wouldn't be able to drive a larger separator (which was why I went with a 30g initially), but having observed the increased airflow from replacing the flex pipe between the filter/impeller with a short straight pipe and generally tightening things up I think it can drive it ok (and really I don't have much to loose at this point - other than some scrap plywood and about $20 for the barrel).

For the larger drum build I believe I'm going to steal galerdude's baffle sandwich idea because that will allow me to try different separator plate materials if I decide to change out for some reason (not that I'm having second thoughts on my choices so far or anything :D).  The thousand cuts sidewall skinned with sheet metal still seems like a win and is pretty easy to do.  I'm really not sure about the baffle though, likely will switch back to the tried and true tempered hardboard - why mess with success by being overly clever twice in a row.

[dabullseye]

Just get a shelix head for your planer

[retired2]

Just get a shelix head for your planer

Thats ironic, because I was going to ask if the planer had a helix head with segmented knives because I've never seen shavings that long from my jointer or planer, and they have 6" and 12" straight knives respectively.  Pine usually produces the biggest chips, but nothing more than an inch or two.

For sure an 11"wide x 7'long board is going to produce a pile of chips, but I think the stringyness of these chips is making it bulk up a lot faster because of all the air space.  It just can't/won't compress on its own. 

Questions:

1) Is the wood wet or green, i.e. not as dry as it should be for normal woodworking?
2) Does the planer have a chipbreaker (I thought they all did)?
3) Is the chipbreaker adjusted properly?

[rumwrks]

1) dry/wet? Its pretty dry - yeah I've seen shavings like this from green turnings, but not from dry wood.  I don't have a moisture meter so I can't say a lot more than - its very light for the size/thickness and drier than any wood you'd get from the local home depot  (not that thats saying a lot) but maybe a wee bit wetter than well cured furniture grade hardwood.  In any case its certainly not straight up green wood.
2/3) chipbreaker/adjusted?  Actually not sure.  I don't believe there are any adjustable parts for this in any case - or if they are its not obvious to me (fyi: its a hammer A3-31 - the knives are quick replace and pretty simple setup).

[retired2]

2/3) chipbreaker/adjusted?  Actually not sure.  I don't believe there are any adjustable parts for this in any case - or if they are its not obvious to me (fyi: its a hammer A3-31 - the knives are quick replace and pretty simple setup).

Didn't realize it is a combo machine.  I know of them, but have never really seen one in the flesh, so they may not have a chip breaker like my old Powermatic Model 100.  It's quite possible that the chips you are seeing are very normal for that machine.

 

[Rick T]

on the planer/jointer combo, I was curious so looked at specs and reviews .. in either mode, cpm is 15K  (5000 rpm and triple cutters) so it's got lots of speed and max depth of cut 5/32" powered with 4 hp. No mention in user reviews of any DC issues and it has 5" dust port.
Try a chunk of hardwood to see if that produces stringy stuff too or not. I'm betting not.
If it did, could you not insert a simple pre-separator ie. cyclone lid on garbage pail type, on the inlet line that would grab the big stuff and the top hat would get the finer material? Not sure what the effect would be on overall efficiency having the 2 devices.

[rumwrks]

Rick: The chips are definitely less stringy on hardwood.  I don't have as big of a piece of that as I do soft at the moment (well, I do.. but I'm not willing to shave that piece down for testing  ::)) so I can't really "push the envelope" as much with that.  I do use a fair bit of softwood work simply because I can get it a lot more readily/cheaper for stuff that doesn't need the stability/appearance (and for some rustic pieces pine just looks good to me).  The dust port is actually 120mm, which is just a smidge less than 5", but I found a local plumbing supply place (or really junkyard but the most awesome junkyard ever - if you're ever in the columbia river gorge area check out Reds Trading Post - no affiliation, just spent a few afternoons wandering around there ;D) that has 5"<->120mm rubber fittings that make great quick connects.  You can also find the fittings online but Reds was actually cheaper.

I'm not sure how much another pre-filter would affect cfm, but it would take up even more space which is already at a severe premium so... yeah filed in the options box but exploring other things first.

I picked up a 55g drum earlier this week on the way home from work (free at the local recycling place, had foaming caustic cleaner so pretty safe once thoroughly flushed - know your chemicals and make friends at the local junkyards) and am working on a new build using that; both because of the greater diameter which I am hoping improves separation as well as the improved capacity.  Filling a 30g drum mostly full rough finishing ONE BOARD made me rethink things a bit there  :o  (ok so it was a pretty rough board, but still...). I'm hoping to have that pretty much complete this weekend and will report how it goes.  My current thought is that the initial build was way undersized for the chip volume.

In the interest of science^(tm) I went ahead and cut up my current top hat some more and opened up the slot to a crazy 2" wide.  The slot width as a function of the separator size is now somewhat ridiculous, but hey I'm not planning to keep this one at this point so why not try it :D.   As expected this threw the fine dust separation even further out the window (still amazingly good considering but down to maybe 90% from the almost perfect it was before), but it actually does seem to be able to most separate the planer shavings now.  I was able to basically stick the hose into a drum full of the shavings I've created so far and suck them all up with only two minor blow by events when a really big clump got caught.  Running the planer actually seems to work pretty well now as it makes little to no fine dust.   This supports my "chip volume vs slot opening area matters when chip volume reaches some critical level" hypothesis.  This also lends hope to the larger separator working better.  I believe that I can probably use a narrower slot on the larger top hat, because I think the required size is at least partially a function of opening area vs chip volume and that the actual slot width only matters as part of that function (after you've crossed the threshold where the chips fit through the slot which is another part of the function).  Its pretty clearly more complicated than that and I know I'm simplifying the heck out of it, but overall opening size does appear to matter for large chip volumes.  So my tentative plan is to figure the current opening area and cut a slot wide enough to have as much area as that into the new top hat to see how that works.  That will I believe either support or disprove my hypothesis (assuming that it ends up wide enough for the chips to fit.. multivariate functions are complicated  :P).  Even if I do have to open up the slot on the larger top hat, it should still separate better than the current setup because of the distance from the impeller inlet to the slot will be so much more (and I have some rough ideas on how the turbulence and indeed even the friction coefficients will change for the better).

I also think that the current top hat may be slightly too large for the barrel (yeah I know, but let me explain) - the current barrel has a bit of a lip (about 3/8" wide) around the inside about 2" below the top where the original top was (I cut the inside of the top off not around the sides - since it retained the more rigid piece on the very top that way).  This actually intrudes slightly into the slot and I think that that actually messes up the airflow based on where the sawdust lands and watching some dust go by it..  In effect this appears to make a narrower slot and perhaps worse may well cause some "kick back" pushing dust/chips back up into the slot.  When I cut the top off of the barrel I did what I could to round this off, but I believe that its still having an impact based on observation.  Its quite possible that had I chosen to use a barrel with smooth sides the current size may have even worked fine.  At this point I have no reasonable way to test how much that actually affects things.  Something else to put in the things that can go wrong file.